Apparatus for the production of pigments.



No. 846,526. PATENTE-D MAR. lf2, 1.907;

l c. P. TOWNSEND. APPARATUS POR THE PRODUCTION GF'PIGMENTS.

" APPLIQATIONgILBD ArR.1s,1992.

"num" [NVE/WUR WITNESSES.-

UNITED sTATpsfTENT OFFICE.-

CLINTON lI. fTOWNsEND, OF WASHINGTON, DISTRICT OF COLUMBIA,

AssIGNORTO ELMER A. SPERRY, OF CLEVELAND, OHIO.

APPARATUS FOR THEPRODUCTlON OF 'PIGMENTS.

Specification of Letters Patent.

Patented March 12, 1907.

Application filed April 18, 1902. Serial No. 103,600r

pigments, and particularly to the productionr I of the h drated carbonate of leadv or White lead, an comprises apparatus for use in such production.

' It has been v proposed heretofore to form such pigments electrol tically but the product has been found to be irregular in composition and quality and deficient in covering power. e

I have discovered that a pigment of uniform grade and exceptionally high covering power may be produced in an electrolytic cell and that the condition essential thereto is a definite circulation ofthe electrolyte successively past the respective electrodes,

and preferably in the direction from the anode past or through the cathode.

In the accompanying drawings I have shown several types of cell to which this princi le is applied. It will be understood that t 1e form ma be varied Within the seo )c of the claims without departing from tile invention.

Iigure 1 shows in cross-section a cell provided with perforated cathodes; Fig. 2, a

cell in which anode and cathode are of plate form, and lig. 3 a form of eell employing p'crvious anodes and cathodes.

Referring to F ig. 1, the cell A is represented as built up of a series of sections (L b c d, secured together by bolts e.

The sections a l; and c- (l clamp between them. the plates C, which may be formed of perforated metal or of Wire-gauze and which a purpose hereafter stated. II represents a filter-press, of any preferred type, communaeating with the outlet-pipes D through pipe.

G and connections F. For this filter-press a settling-tank or other separating device may be substituted. The filtered electrolyte passes from the press H into the tank I and is thence returned to the cell through pipe J andeasing K. As a means for effecting the circulation ofthe electrolyte I have illus'- trated a propeller M, vmounted upon a shaft L and driven by a pulley N. The shaft L is preferably hollow, and through it carbon dioxid may be introduced into the cell, thereby assisting in the circulation of the electrolyte and regenerating the same.

h represents the pipe for introducing water into the electrolyte. Such water is .preferably introduced, as shown, through thefilterpress and employed for washing the pigment. The valves E are provided in the pipes D, and by opening them to a greater `or less ex tent a rapid and repeated circulation may be secured through the cell, a ortion only of the circulating electrolyte eing continuously drawn oil' through the filter-press.

In the construction shown in Fig. 2 the cell A is provided with a bottom section c in the Aform of an inverted Wedge in order that no pigment may collect in the lower portion of the cell. The electrodes B' C are Vplates placed, respectively, in the neighborhood ofthe inlet and outlet of the cell,

In the construction shown in Fig. 3 a tank A is provided with a false bottoni T, which serves to support the divided anode B2. The cathode Cz is 1n the form of a perforated plate, transversely of the tank atits upper portion. '.lhe electrolyte overilowing through the cathode is collected in the trough C) and con ducted through the pipe P to the separating devices. The clear electrolyte is returned to the cell by the centrifugal pump In this construction the carbon dioxid required for regeneration of the electrolyte is preferably introduced at the axis of rotation of the centrifugal pump through the pipe R. Introduced at this point it serves to aid the circulation of the electrolyte. The anode B2 is represented as consisting of lead individed forni and may be in the form of bars or fragments of lead or of lead sponge or lead in any intermediate forni of subdivision.

It will Je seen that in Fig. 1 the circulation IOC .of the electrolyte roceeds from thev anode cathode, but that the pigment oiinsoluble com ound formed at the anode detaches itself therefrom and is carried upwardly by the electrolyte past or through the cathode vand thence to a region outside the iield of electrolysis.

It will be further seen that in the constructionsshown in Figs. 1 and 3 the area of the' cathode is greatl reduced as compared with that ofthe ano e. This is of great as sistance in preventing the formation of lead sponge by reduction of theA pigment not only because Ithe speed of circulation through the cathode is thereby increased and the pigment prevented from adhering to it, but because the electrolytic reduction itself roceeds more slowly when the cathode area is relatively small and the current ,density relatively'high.

, In operation a lead anode is employed and an electrolyte consisting of any salt whose acid radical forms a soluble com ound with lead. To this solution is adde a` soluble carbonate. Q 'In practice I have found a' mixM ture of sodium nitrate or acetate and sodium carbonate in proportions approximating ten to one to constitute a satisfactory electrolyte. The current density depends to some extent on the speed of circulation v'of the electrolyte, a higher current density being em loyed, as this circulation is more rapid.

o regenerate the electrolyte, it is necessary to add thereto continuously or at inter yvals carbon dioxid and water in quantity equal to that removed" by the pigment. The carbon dioxid may be employed, as shown, to aid or as the sole agent for effecting the i circulation of the electrolyte.

I claim-4 1. In a cell for the productionof pigment, an anode, a cathode of relatively reduced area, and means for circulating the electrolyte successively past the electrodes.

2.- In combination, an electrolytic cell, for the production of pigment, a separator for the pigment produced therein, and an injec tor arranged to circulate the electrolyte successively through the cell and the separator.

3. In combination, an electrolytic cell, a separator, conduits between said cell and separator, and an injector arrangedl to aid the circulation of the electrolyte between the cell and the separator.

4. In a cell for the production of white lead, an anode of lead and a suitable cathode, and means for circulating the electrolyte upwardly between the electrodes and thence to a point lexternal to the electrolytic field', substantially as described'. x

5. In a cell for the production of white lead, an anode of lead and a suitable cathode, means for circulating the electrolyte upwardly between the electrode/s and thence to a point outside the electrolytic field, means for separating the pigment, and means for returning the electrolyte to the electrolytic field, substantially as described.

' 6. In a cell .for the production of white lead, an anode of lead and a suitable cathode, means for circulating the electrolyte in a tortuous'path withinA the cell and thence to a point outside the electrolytic field, means for separating the pigment, and means for returning thc electrolyte to the electrolytic field, substantially as described.

In testimony whereof I affix my signature in presence of two witnesses.

CLINTON P. TOWNSEND.

' Witnesses:

PERCY B. HILLS, EUGENE A. BYRNEs. 

